m8 built in -0.5 diopter

[jaapv]

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That is not quite correct, Vinay. The RF patch is situated at a virtual distance of 2 m. For focussing purposes that is the fixed diopter correction.

[pekem]

Sadly, the facts contradict the foregoing. The Leica M viewfinder is, aside from a reduction in magnification, like looking through a window. You need whatever strength of eyeglasses you need for whatever subject distance as you would if there were no camera before your eye. Those who wear single-vision eyeglasses can abscond with a single corrective diopter, but those who require bi- or multi-focal eyeglasses cannot, moreso the larger the disparity is between near and far-distance Rx. An SLR is completely different. There the entire image is focussed on a single plane (the focussing screen) and one simply need find the diopter that permits seeing a sharp image on the screen. For those with strong multi-focal Rx, the best option is "progressive" eyeglasses and no corrective diopter on the Leica. One then simply adjusts one's view of the finder so that the appropriate area of eyeglasses are used for various subject distances, just as in daily sight.

 

And I thought it was going to be easy for someone to provide an answer! I am now totally confused.

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[jaapv]

And I thought it was going to be easy for someone to provide an answer! I am now totally confused.

 

The answer is : fixed diopter correction works.See post 21. and Howard's post.

[Guest tummydoc]

That is not quite correct, Vinay. The RF patch is situated at a virtual distance of 2 m. For focussing purposes that is the fixed diopter correction.

 

However, the images of the subject seen through the patch are not situated at a virtual distance, therefore whilst a single diopter correction is sufficient to see a sharp outline of the rangefinder patch itself (as well as metering diodes and other display icons), it is not sufficient for extremely precise focussing for the majority of people with multi-focal corrective needs. It's been discussed at length over lunch with a Leica-using colleague who supports his addiction through the occasional practise of opthalmology

[jaapv]

If that were relevant, Vinay, nobody wearing varifocals would be able to use a rangefinder. However, from daily practice and as somebody who needs three different strengths, I can assure you that a single diopter for the distance of 2 m. does the trick.

[Guest tummydoc]

Humans' eyesight is infinitely variable, the facts are not. There is anecdotal evidence to support almost any opinion. The Leica M rangefinder is more forgiving of minor lack of visual acuity than a reflex. At least it was, before 100% crops and pixel-peeping became the gold standard in judging every happy snap

[jaapv]

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I believe I'm in good company when I insist: "but it still works" . I have no desire to be burned at the stake though

[carstenw]

Vinay, I don't know why you are getting so vicious about it? This isn't "anecdotal evidence", Leica *documents* it as being at a distance of 2m. Guenter Osterloh's "Leica M" book has it on page 48 (the German version, the English page number will be similar). Osterloh was a product manager and part of the Leica M design team for decades. I don't know where your friend gets his information, but his high education doesn't seem to have rescued him from being wrong.

[Guest tummydoc]

I'm not being vicious, unless the definition on this forum is "anyone who disagrees with prevailing myth" Anyone who is far-sighted can quickly verify for himself simply by removing his eyeglasses, that he will be able to see far subjects far more sharply through the M finder than near subjects. The converse will be true for the person who is short-sighted. Easy to verify, so simple a cave man could do it I suspect that those who believe that a single diopter strength can mitigate the M's finder at all distances, are those who are neither exceedingly short- nor far-sighted. As I said, it's a relative matter.

[fursan]

i went to the optician last night. took my m8 with me. he said no pictures allowed!

the end result, he checked, i checked, the camera checked. he told me i needed

specs for long distance. i told him, i had made these specs from him. he said 'oh'.

 

we started again on our odessy to prepare to use the m8, once again. he said i

had astigmatism, and therefore the camera vf has to be cylindrical! i said the camera

cannot be modified. he looked at the camera..he said it is not japanese!

 

i came back with my m8 and my reading specs.

 

i will try to find a neurologist!

[carstenw]

Hahaha, great story (which is your first name and which is your last? I forget how Arabian names work).

 

Vinay, I just looked through my M8, and both far and near are sharp, although near is a bit sharper for me... I don't know what this proves though.

 

The M8's viewfinder is an optical system, not a flat piece of glass, and it places the virtual image plane at a distance of 2m. This means that you need the prescription with which you can focus at 2m to be able to see the objects in the viewfinder sharply. This is independent of where the lens is focused or how far you are looking, because the viewfinder doesn't focus itself, it stays the same. Only the rangefinder patch changes, being mirrored in.

[fursan]

Carsten, name is Fahim.

 

i did not mention that i took my zeiss zi with me too. that remained untested during

this journey of discovery.

 

now i can pack my m8 to solms without missing it too much, and ask them to

change the vf!!

 

take care.

 

 

Hahaha, great story (which is your first name and which is your last? I forget how Arabian names work).

 

snip

 

.

[carstenw]

What will the trip to Solms fix? Wasn't the conclusion that you needed a diopter which corrects for astigmatism? This should be done by an optician... Full circle. I imagine that an optician could insert the proper lens into a Leica diopter frame.

[fursan]

Carsten, 'lux problem. was trying to hold off as long as possible. seriously, though

i went to a consultant optholmogist today. five minutes with complex equipment

and i got a +1 cylinderical specs for the m8.

 

can focus a hair now!

best.

 

 

 

What will the trip to Solms fix? Wasn't the conclusion that you needed a diopter which corrects for astigmatism? This should be done by an optician... Full circle. I imagine that an optician could insert the proper lens into a Leica diopter frame.

[wlaidlaw]

I think the answer to the image distance, if I remember correctly from my university physics is that the Leica shows a virtual image not a real image like you see on an SLR. A virtual image can have an image distance, which you can measure by looking at a two pin heads one through the VF and one directly and then moving the direct pin head until it appears to be above the VF one. Someone who has done physics more recently than me (Isaac Newton was my Professor) may be able to put this better than me.

 

Wilson

[Guest tummydoc]

 

Vinay, I just looked through my M8, and both far and near are sharp, although near is a bit sharper for me... I don't know what this proves though.

 

It proves that I am right and you are wrong If there was a single "virtual distance" as you've been insisting, there would be no difference between near and far, they would be equally sharp or unsharp, depending upon how far your eyesight is from being able to focus that 2m "virtual distance" sharply. The difference you did see would be proportionately greater the further your eyesight from 20:20.

 

The M8's viewfinder is an optical system, not a flat piece of glass, and it places the virtual image plane at a distance of 2m. This means that you need the prescription with which you can focus at 2m to be able to see the objects in the viewfinder sharply.

 

The "optical system" as you put it, is de-magnification and a half-silvered prism to allow the rangefinder, framelines, and display diodes to superimpose. That projection of the rangefinder patch, framelines, and finder display are the only things that are fixed at a "virtual distance". The view of the outside world is simply a de-magnified version of looking through a clear window glass. The fallacy is that the only requisite for precise focussing is to be able to see the rangefinder patch (which is at 2m virtually) clearly. In truth, one must also be able to sharply differentiate objects within the rangefinder patch, and that will require different diopter strengths depending upon their distance. The greater the disparity between one's close-distance Rx and far distance Rx, the more pronounced the effect will be noticed.

[Shootist]

I think the answer to the image distance, if I remember correctly from my university physics is that the Leica shows a virtual image not a real image like you see on an SLR. A virtual image can have an image distance, which you can measure by looking at a two pin heads one through the VF and one directly and then moving the direct pin head until it appears to be above the VF one. Someone who has done physics more recently than me (Isaac Newton was my Professor) may be able to put this better than me.

 

Wilson

 

Wilsson you are totally correct. When you look through the eye piece you are NOT seeing straight through to the front of the cameras viewfinder window. There is a whole series of prisms that take what the VF & RF patch is seeing and project it on a viewing screen that you are looking at throught the eye piece.

I dropped one of my M3's and broke the VF. You could no longer see through it except the rangefinder patch. The prism for the VF broke off it's mount.

[carstenw]

It proves that I am right and you are wrong If there was a single "virtual distance" as you've been insisting, there would be no difference between near and far, they would be equally sharp or unsharp, depending upon how far your eyesight is from being able to focus that 2m "virtual distance" sharply. The difference you did see would be proportionately greater the further your eyesight from 20:20.

 

Not necessarily. I am using a -1.0 diopter, and this is actually to strong for my eye They don't make the exact one I need, sadly.

[Guest tummydoc]

When you look through the eye piece you are NOT seeing straight through to the front of the cameras viewfinder window. There is a whole series of prisms that take what the VF & RF patch is seeing and project it on a viewing screen that you are looking at throught the eye piece.

I dropped one of my M3's and broke the VF. You could no longer see through it except the rangefinder patch. The prism for the VF broke off it's mount.

 

You most certainly are seeing straight through...the prism you speak of is semi-silvered for expressly that purpose. Once the halves separate however, it is impossible to see through. Perhaps if you spoke with one of the Leica repair shops, as I have done on countless occasions, they could go into greater detail.

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Hallo,

Look here: Leica M

[ho_co]

This is getting fun! Everybody is screaming at everybody else, "You're wrong!" In fact, everybody is pretty nearly correct. So we can all get in the hot tub together--though not with the M8.

 

And I thought it was going to be easy for someone to provide an answer! I am now totally confused.

You use whatever is your medium-to-far distance correction if you wear glasses. It _is_ simple, though a little of what everyone says is correct.

 

However, the images of the subject seen through the patch are not situated at a virtual distance, therefore whilst a single diopter correction is sufficient to see a sharp outline of the rangefinder patch itself (as well as metering diodes and other display icons), it is not sufficient for extremely precise focussing for the majority of people with multi-focal corrective needs. It's been discussed at length over lunch with a Leica-using colleague who supports his addiction through the occasional practise of opthalmology.

Wowsers, Vinay! "It's been discussed"? Passive? Sounds as if you're disowning it! But you are generally correct.

 

Humans' eyesight is infinitely variable, the facts are not. ... The Leica M rangefinder is more forgiving of minor lack of visual acuity than a reflex. At least it was, before 100% crops and pixel-peeping became the gold standard in judging every happy snap.

You've made some very good points, particularly in the last two sentences. However, for me, that "infinitely variable" human eyesight has dropped to, what, aleph-sub-one, the least of the three infinities, at most. And if you think facts aren't variable, look at the Bush administration.

 

But you bring up another good point: The best way to focus the rangefinder is to focus once. Just bring the two images quickly into superposition and stop playing with it. Usually, one's 'first best guess' at aligning the images is more than good enough. It's often better than the result of swinging through to each side and reducing the amplitude of the swing each time. (This is the opposite of best focusing practice on a telescope, SLR, microscope etc.)

 

 

I think the answer to the image distance, if I remember correctly from my university physics is that the Leica shows a virtual image not a real image like you see on an SLR. A virtual image can have an image distance, which you can measure by looking at a two pin heads one through the VF and one directly and then moving the direct pin head until it appears to be above the VF one. Someone who has done physics more recently than me (Isaac Newton was my Professor) may be able to put this better than me.

Thanks, Wilson, for reminding of that; that's something I was taught in my first days at Leica (though they didn't mention the pins). The virtual image is the whole secret to the problems we're having. (Well, aside from our various personalities. )

 

A virtual image; and it is diminished by the 0.68 magnification of the finder. That same 'minification' reduces the apparent distances between real-life objects when viewed through the finder.

 

Vinay is right that the objects are at various distances, but Carsten is right that they hardly seem to be, because the discrepancies are so greatly reduced. We do need to focus our eyes differently or use different parts of our glasses, but the difference is quite small, and as a simple rule of thumb, you need the correction that allows you to focus on a 2 m distance, since that is where _all_ the important parts of the finder are projected, viz RF patch, frames, numeric displays. From there for most if not all of us, it's pretty easy to focus on other objects through the finder.

 

The M8 VF works pretty much like a window connected to a rangefinder by means of a semi-silvered prism, _except_ that it's a pretty strange window. More like a fun-house mirror that reduces the size of reflections (in this case transmissions) by a factor of 0.68x.

 

So all the arguments above are right either in fact or in practice. Be nice to each other now, because we can all say, "I was right and he was wrong; he just didn't approach the matter like me!"

 

Fahim--

I also have astigmatism, and of course no spherical correction (including the M diopter) can accommodate that. So I always figure that since I need glasses for the astigmatism anyway, there isn't any use in getting a diopter for the camera.

--HC